---

Jim, diameter isn't really a variable - you get a prop which is the proper diameter for the motor, and that's it. I would be inclined to drop down in pitch, possibly all the way to a 13, and see how that works for you. With your usage model where you can't go that fast much of the time anyway, that will give you a nice low gear for power, and it should get you up in the RPM range where that motor will sing.

For reference, the trade-in for a different pitch policy is standard for Power-Tech - one of the things I like about them.

Tim